A tofu pack is sealed by putting tofu into a plastic pack container and bonding a plastic film onto the pack container, wherein bonding is completely performed due to the nature of the goods. Therefore, since it is very difficult to peel off the bonded portion of the film by hand, the tofu pack tops the package which is most difficult to open. Though the tofu is heavy and easy to get out of shape, the tofu pack, while it is put in a show case, even if it is carelessly handled, the pack is not damaged and does not lose its sealing function. However, when the tofu pack is opened, it is necessary to cut and open the film with a knife or a kitchen knife. Though a container which satisfies the requirements for perfect sealing and readiness of unsealing that are in conflict with each other is best, a container satisfying such requirements has not yet been achieved.
Technology of filling and packing the contents has been disclosed in, for example, JP-A-10-119936. Herein, a peeling portion which is bondless to a lid material is partially formed in a base material, and the peeling portion is pinched with fingertips to open the pack. This peeling portion provides a start of unsealing. However, even in case that the bondless peeling portion is provided at the corner of the pack container, it is difficult to think that unsealing of the tofu pack in which the film is completely bonded is facilitated. This is because the tofu pack cannot be held forcibly since the material of the container is soft. Further, a package container which holds pickled vegetables including pickle, which has been disclosed in JP-A-2002-211647, has a constitution in which a label that covers an opening and closing door adheres onto a surface of a lid body in order to obtain sufficient airtightness and make unsealing of the container easy. However, in this case, the pickle may leak from the opening and closing door surrounded by notches, and it is also difficult to take out the tofu without getting out of its shape because the opening and closing door is considerably smaller than the container body.
Therefore, this inventor has developed a sealed container with a snap portion (JP-A-2006-21791) in which a flange portion surrounding an opening portion of a pack container is firstly snapped thereby to take out the contents readily without peeling off a film at a firmly sealed portion. In this invention, a snap groove is formed in order to snap the flange portion. However, because of structure in which the groove portion exists, there is possibility that the flange portion will bend when a container maker forwards goods. Further, since there is also possibility that the flange portion will bend in a food packing process during the display at the shop, it is necessary to pay attention to handling of the container. Even if the flange portion snaps at the groove portion, there is no anxiety that the contents will leak out. However, the fact that the flange portion has been bent causes a sense of unease. Further, in order to snap the flange portion, it is necessary to bend the flange portion completely from end to end and at about 180°. However, even if this is explained, it can be difficult for the user to understand. In case that there is difficulty in unsealing, there is also possibility that the container will break and the contents leak out from the unexpected portion. Further, there is room for such improvement in that the flange portion cannot be snapped when occasion demands.